Nonstoichiometric algorithm of calculations of simultaneous chemical and phase equilibria. 1. Influence of a method modeling nonideality of systems on the calculated equilibrium composition at low pressure

Abstract

A nonstoichiometric algorithm for the calculation of simultaneous chemical and phase equilibria (CPE) in multicomponent nonideal systems is presented. This algorithm provides an implementation of the intermediate method for nonideal systems based on the ideal-system BNR algorithm (Smith and Missen, 1982). This implementation is used for calculation of CPE of strongly nonideal systems (the mixtures in esterification of acetic acid with ethanol or methanol), and the results obtained for different methods modeling the system nonideality (ASOG, original UNIFAC, UNIFAC modified by Larsen, the Wilson equation, regarding or disregarding organic acid association in the vapor phase) are compared. It is shown that the differences in calculated equilibrium compositions resulting from the different nonideality models are extremely significant. The method of verification of calculated equilibrium composition is presented.

Modeling of Simultaneous Chemical and Phase Equilibria in Esterification of Acetic Acid with Ethanol in High-Pressure Carbon Dioxide

“…These two systems were also not very precisely described by the methods based on the activity coefficients γ i . 3 The experimental amounts of the individual elements in the feed and product 1 are similar but not exactly the same. Since the amount of gas phase is small, the disagreements in the elemental balance can have quite significant influence on the differences between the calculated and measured values of the individual component concentrations.…”

Nonstoichiometric Algorithm of Calculation of Simultaneous Chemical and Phase Equilibria. 2. High-Pressure Hydration of Propene to 2-Propanol

“…The implementation of the BNR algorithm to tackle nonideal systems consists of the presentation in an explicit form of expressions describing chemical potentials of every real component (Wyczesany, 1993). In the case of the EOS approach this expression has the following form for both phases: ±i_ RT µ.…”

“…If additionally the resulting product forms in mainly the liquid phase, simultaneous chemical and phase equilibria are to be determined. A very powerful tool to solve such problems is the implementation of the BNR algorithm (Wyczesany, 1993) describing the nonideality of the system using EOS with interaction parameters depending on temperature as well as on the composition. These parameters are to be estimated on the basis of published data.…”

“…The main goal of this paper is to present the methodology of the calculation of equilibrium composition in two-phase systems consisting of strongly nonideal components at high pressures. The implementation of the intermediate method for nonideal systems based on the ideal system Brinkley-NASA-RAND (BNR) algorithm (Wyczesany, 1993) has been used as the basic procedure. The nonideality of the system was described using three methods appropriate for systems containing gases whose critical temperatures are below the equilibrium temperature.…”

Chemical Equilibria in the Process of Etherification of Light FCC Gasoline with Methanol

“…The original computational program written on the basis of the BNR algorithm can be applied to ideal systems only. In this paper the developed version of tbat program was used (Wyczesany, 1993). This version can be applied to the calculation of simultaneous chemical and phase equilibria, in multicomponent and multiphase systems.…”